The applications of light-emitting diodes are extensive, such as optical display devices, traffic signals, data storing devices, communication devices, illumination devices, and medical apparatuses. It is important to increase the brightness of light-emitting diodes, and to simplify manufacturing processes in order to decrease the cost of the light-emitting diode.
In general, a conventional nitride-based light-emitting device includes a nitride-based buffer layer composed of group AlGaInN and formed over a sapphire substrate, and a nitride-based epitaxy process is undergone on the nitride-based buffer layer to form a nitride-based light-emitting device. Due to the mismatching of the crystal lattice constants, the dislocation density (which affects the quality of the conventional nitride-based light-emitting device) cannot be decreased efficiently.
Therefore, in order to improve the quality of the conventional nitride-based light-emitting device, the conventional nitride-based epitaxy process is mended as a two-step growth method. The two-step growth includes utilizing low-temperature (500 to 600° C.) GaN for forming a buffer layer, and a heating process (reaching a temperature of 1000 to 1200° C.) for crystallization. After the two-step growth, an epitaxy process for each epitaxy stack layer is proceeded. The thickness and temperature of the buffer layer, the recovery of the heating and re-crystallization processes, plus the ratio and flow rate of gas for each reaction must be controlled precisely, thus the manufacturing process becomes complicated and difficult, and the manufacturing efficiency cannot be increased.
In addition, the nitride-based light-emitting device can be further connected to other components in order to form a light emitting apparatus. The nitride-based light-emitting device may be mounted onto a submount with the side of the substrate, or a solder bump or a glue material may be formed between the submount and the nitride-based light-emitting device, therefore a light-emitting apparatus is formed. Besides, the submount further comprises the circuit layout electrically connected to the electrode of the nitride-based light-emitting device via an electrical conductive structure such as a metal wire.